Fuel control system



June 20, 1961 F. c. REGGIO FUEL CONTROL SYSTEM Original Filed Feb. 3,1939 3 Sheets-Sheet 1 lNvl-:NToR

le/f

June 20, 1961 Original Filed Feb. 3, 1959 F. c. REGGIO FUEL CONTROLSYSTEM Il 3 l 74 u2 |06 AIHIM 3 Sheets-Sheet 2 IN VEN TDR new June 20,1961 F. c. REGGIO 2,989,043

FUEL CONTROL SYSTEM Original Filed Feb. 3, 1939 3 Sheets-Sheet 3 'ff- W2,989,043 'FUEL CONTROL SYSTEM Ferdinando Carlo Reggio, Tampa, Fla. (R0.Box 692, Norwalk, Conn.)

Application July 27, 1943, Ser. No. 496,296, now abandoned, which is 'adivision of application Ser. No. 254,355, Feb. 3, 1939, now abandoned.Divided and this application .lune 7, 1956, Ser. No. 591,511

20 Claims. (Cl. 123--119) The present application is a division of myapplication Serial No. 496,296, filed luly 27, 1943, now abandoned,which is a division of my application Serial No. 254,355, filedlFebruary 3, 1939 now also abandoned.

'I'his invention relates to fuel supply systems for internal combustionengines and in particular to mechanisms for the control of the relativeproportion of fuel and air composing the combustible mixture of internalcombustion engines.

It is chiefly although not exclusively, applicable to spark-ignitionaircraft engines including a fuel injection system discharging liquidfuel into the engine cylinders or the engine induction manifold.

Spark-ignition engines having a -fuel injection system are usuallyprovided with means for controlling the fuel supply and means forcontrolling the air supply of the engine. It is important that theadjustment of the fuel and air control means be interrelated so that theengine cylinders may be charged with a combustible mixture having asuitable fuel-air ratio. Extensive experimental work connected inparticular with the development of aircraft engines has shown that themost suitable value of fuel-air ratio varies with the engine operatingconditions such as, for example, the air pressure or density in theinduction manifold, the speed of the engine, the properties of the fuel.The fuel-air ratio corresponding to best economy operation required, forinstance, in a cruising airplane, is dierent from that corresponding tomaximum power operation which is necessary for take-off. Furthermore,enrichment of the combustible mixture may be desirable when thetemperature of the engine cylinders attains or exceeds a safe limit. Itis therefore advantageous that, while the means for controlling theengine supply of one of the components of the combustible mixture(eitherithe air or the fuel). may be directly actuated by the operator,the supply of the other component may be controlled by automatic meansso as to vary the fuel-air ratio as a predetermined function of certainengine operative conditions. l

One of the objects of the present invention is to provide, incombination with an internal combustion engine including fuel meteringmeans, means whereby the fuelair ratio of the combustible mixture may beautomatically `controlled and caused to vary as a predetermined functionof certain engine operative conditions such las, for instance, inductionair density or cylinder air charge, engine speed, engine cylindertemperature.

Another object is to provide, in combination with a spark-ignitionengine having a fuel injection system and in which the pilot controlsthe engine supply of one of the components of the combustible mixture,automatic devices for controlling the engine supply of the othercomponent, including mixture control means whereby the fuel-air ratio ofthe combustible mixture is determined by the adjustment of said mixturecontrol means and for a given adjustment thereof is substantiallyindependent of the engine operative conditions.

Such mixture control member may be adjusted by the pilot or, accordingto `further objects of the "invention, by automatic devices.

The above and otherobjects of the invention be ap- Patented .lune 2),1961 parent as the description proceeds; and while I have illustratedand described the preferred embodiments of the invention as they nowappear to me, it will be understood that such changes may be made asfall within the scope of theappended claims. In the followingdescription and in the claims various details will be identiiied byspecific names for convenience, but they are intended to be as genericin the application as the art will permit.

In the drawings: FIG. l is a sectional elevation of a fuel meteringpump; FIG. 2, in part a section on line 2--2 of FIG. l, shows two fuelmetering pump units together with means for feeding fuel at variablepressure thereto; FIG. 3 diagrammatically indicates a fuel metering pumpapplied to a radial aircraft engine and control means therefor; FIG. 4shows a modification of the fuel pressure regulating means of FIG. 2;FIG. 5 diagrammatical'ly illustrates means responsive to the inductionsystem pressure for adjusting the fuel delivering; FIG. 6 indicatesmeans similar to those of FIG. 5 but simultaneously responsive topressure and temperature in the induction system; FIG. 7 is a partialmodication of FIG. 6 showing a resilient means having a nonlinearcharacteristic; FIG. `8 is a partial modification of the pressureresponsive means of FIG. 6; FIG. 9 is a further modification of the samemeans; FIG. 10 is a partial modification indicating the application ofthe device of FIG. 6 to control a conventional fuel pump; FIG. l1partially shows an airthrottle regulating device; FIG. 12 indicates amodification of IFIG. ll; FIG. 13 illustrates the application of thecontrol means of FIG. 1l to a conventional fuel pump; FIG. 14 is adiagrammatic View of means responsive to an engine operating temperaturefor controlling the fuel-air ratio; FIG. l5 shows means responsive tothe induction pressure for controlling the fuel-air ratio; and FIG. 16illustrates speed-responsive means for varying the fuel-air ratio.

As shown in FIG. 1, a fuel pump 1 has a plunger 2 reciprocating ain abarrel 3 having a port 5. At its upper end, beyond an annular groove 6,the plunger 2 has edges 7, 8 which limit the plunger surface in contactWith the bore of barrel 3. Below groove 6 and at suitable distancetherefrom plunger 1 has a splined portion 10 formed as a pinion andmeshing with a rack 11 formed in a piston 12 slidable in a cylindriccavity 15 of barrel 3. The lower 'end of plunger 2 is urged by a spring1.6 against a lifter 18 operated by a cam 19 driven by the engine. Acupshaped cap 20 screwed on the upper end of barrel 3 closes the pumpingchamber 22 and provides, between barrel and cap, an annular chamber orreservoir 24 communicating through port 5 with pumping chamber 22 andthrough annular apertures of very small area provided between barrel 3and cap 20 with annular chambers 26 and 27. A gasket 21 prevents fuelleakage between barrel 3 and cap 26.

Annular chambers 26 and 127 communicate with chamber 2S at one end ofcylindric cavity 1S by means of ducts 30, 31, 32 and 33. Chamber 29 atthe opposite end of cavity 15 communicates with reservoir 24 throughduct 35. At the upper end of pumping chamber 22 a spring loaded checkvalve 36 admits fuel, through duct 38, annular groove 39, duct 40 andhollow fastening bolt 41, to conduit 42 leading to the nozzle. A spring44 acting on piston 12 is provided in chamber 28. In the preferredembodiment, a multicylinder engine has number of pumps 1 each arrangednear the corresponding cylinder. As indicated in FIG. 2, a fuel transferpump 48, connected through pipe 51 with a fuel tank, not shown, deliversfuel to a conduit `45 which communicates, through a hollow bolt similarto bolt 41 and a duct 47, with chamber 29 and reservoir 24 of each pump1, which chamber 28 of each pump communicates, through a duct 33 andanother hollow bolt, with a fuel return line 49 and a pipe 50 leadingfuel back to the tank. Between outlet and inlet ports of transfer pump48 a bypassis provided, controlled by ya pressure regulating valve1ncluding a piston 52 urged by a spring 53 Whose load may be varied byscrewing or unscrewing the threaded cap 54 provided with a lever arm 55.A groove 56 and a duct 57 lead fuel leakage back to return line 49.

As the delivery of transfer pump 48 is substantially larger than thetotal requirement of pumps llunder all operating conditions, excess fuelflows past regulating valve 52, and the fuel pressure in feed line 45and in chambers 29 of pumps 1 will therefore be controlled by the loadof spring 53 and the adjustment of lever 55. Changes of pressure inchamber 29 axially displace piston 12 and vary the angular adjustment ofplunger 2. In FIG. 3 -a pump 1 is shown equipping an aircraft engine ofthe radial type having a cylinder 60 to which air supplied by asupercharger 61 is fed through induction pipe 62. A throttle valve 63controlled by a lever 64 and control lever 65 is provided to regulatethe air charge. A second control lever 66 adjusts the angular positionof lever 55 shown in detail in FIG. 2. Fuel conduit 42 communicates withnozzle 70 through which fuel is injected into pipe 62 during part of thesuction stroke of cylinder 60. Nozzle 70 may obviously be mounted in anyother suitable position, such as near the intake cylinder port or valve,or inside the cylinder.

In the position shown in FIG. 1, the plunger 2 is at the end of itssuction stroke and has uncovered the port 5 allowing fuel to flow intothe pumping space 22. As the plunger rises, operated by cam 19, thesurface comprised between edges 7 and 8 covers the port 5. The pressurerises rapidly in space 22 and lifts the check valve 36 and throughnozzle 70 fuel is injected in the i11- duction pipe 62 and carried bythe incoming air into the cylinder 60. The injection continues untiledge 8 uncovers port 5 which now functions as a pressure relief portthrough which the remaining fuel displaced by the plunger is bypassedinto the reservoir 24.

While the engine is in operation, the fuel pressure in grooves 26 and27, substantially the same as in chamber 28 and fuel return line 49, islower than in reservoir 24, and a continuous flow of fuel is ventedthrough the annular `apertures of very small area provided betweenreservoir 24 and grooves 26 and 27. T he volume flow- 1ng through anorifice under a given difference of pressure being for a gas or a vaporseveral times greater than for a liquid, the area of said apertures maybe made such that under the existing difference of pressure vapor or gasseparating from the fuel in reservoir 24 can be eliminated therefrom,while only a relatively small volume of liquid fuel escapes through saidapertures. As said annular apertures surround port 5, whatever theorientation of pump l may be relative to the vertical line, gas or vaporbubbles can be vented from reservoir 24 at a point higher than port 5,thereby reducing the risk of such bubbles being drawn into pumping space22 where they might interfere with the correct operation of the pump.

The plunger 2 being provided with at least one substantially helicalcontrol edge, the duration of its effective delivery stroke and therebythe weight of fuel delivered per stroke may be varied by a turningadjustment of the plunger obtained by adjusting the fuel pressureregulating valve 55. In the preferred embodiment of the invention thefuel supply system is so arranged that changes in fuel pressure inconduit 45 and the corresponding variations in delivery per cycle ofpumps 1 are proportional. Owing to the fact that axial displacement ofvalve piston 52 corresponding to changes in the fuel flow through thevalve is very small, and the spring 53 is very flexible, changes in theload of the latter due to said axial displacement of piston 5'2 arepractically negligible, variations of angular adjustment of lever 55 andcorresponding changes of fuel `delivery per cycle of pumps 1 may also beconsidered proportional. To secure proper venting and cooling of pumps 1under all conditions, it is convenient that the zero delivery angularadjustment of plunger 2 correspond to a predetermined pressure in feedline 45 higher than in fuel return line 49. FIG. 4 indicates analternative form of pressure regulating valve wherein a highly resilientspring 73 is adjusted to exert on valve piston 72 a load which balancessaid predetermined fuel pressure that corresponds to said zero deliveryangular adjustment of plungers 2. Since, as previously stated, themaximum axial displacement of valve piston 72, under extreme operatingvalues of fuel ow through the port controlled by piston 72, is verysmall and the spring 73 is very flexible, if no load is applied to theouter end of piston 72, the fuel pressure in conduit 45 is maintained bysprings 73 substantially constant at said predetermined valueindependently of changes of delivery of fuel transfer pump 48, and theplungers 2 are maintained angularly adjusted for zero delivery. If afurther load is applied to valve piston 72, for instance by means oflever 74, the fuel pressure in conduit 45 is increased beyond saidpredetermined value and the plungers 2 are turned to deliver thecorresponding quantity of fuel. Therefore in the preferred embodiment ofthe invention, as already pointed out, the fuel delivery per cycle ofpumps 1 is proportional to the load transmitted to piston 72 by lever74.

One of the advantages of this fuel supply system is that control of fueldelivery is obtained by adjusting the pressure regulating Valve, whichmay be performed by automatic devices of very little energy, especiallyif compared With fuel pumps of the same general character in whichturning adjustment of the pump plunger is obtained fb-y means of linkspositively inter-connecting all plungers with the control means,whereby, if a plunger is scored and cannot be turned in its barrel, itmay prevent the adjustment of all other pump plungers and put the engineout of control. In the fuel supply system which is herein described, afailure occurring to one pump does not interfere with the operation ofthe other pumps.

The arrangement of FIG. 3 in which air and fuel supplies are controlledby distinct levers 65, 66 is not suitable for spark-ignition engines,which require a combustible mixture having definite fuel-air ratio. Amore convenient arrangement, shown in FIG. 5 includes pressureresponsive means, such as a resilient and evacuated bellows 75surrounded by fluid having the same pressure as in the induction pipe62, transmitting to a fuel pressure regulating valve 72, through a link76 and a lever 74, a load proportional to the induction pressure. Theoperating distance of link 76 from the fulcrum of lever 74 may be variedby lever 79 connected with control lever 78 whereby the ratio of fueldelivered per cycle to induction pressure depends on the adjustment ofcontrol lever 78 and is independent of engine operating conditions oraltitude. This simple device, applied to an internal combustion enginein which the induction temperature, or temperature of the air in enginemanfold 62, is substantially constant, as it may be the case when anintercooler is used, and in which the cylinder air charge isproportional to the induction pressure, automatically controls the fueldelivery so as to maintain, for each adjustment of lever 78, acorresponding constant value of fuel-air ratio in the combustiblemixture. This device is intended to be used in combination with meansfor controlling the air supply of the engine, such as, for instance,that indicated by numerals 63 to 65 in FIG. 3, by which the inductionpressure in manifold 62 may be regulated. The main control of the enginethrottle lever 65, and the fuel-air ratio may be adjusted by mixturelever 78, either by the operator or by automatic devices. In combinationwith engines in which the variations in induction temperature are smallbut not negligible, it may be convenient in order to compensate forvariations in air density and engine air supply due to small changes oftemperature in manifold 62, to provide in bellows75 a certain weight offluid, the pressure of which increases with the temperature, thearrangement being such that the temperature of bellows 75 be the same asin pipe 62 whereby, fora given pressure in said pipe, the fuel deliveryis reduced ywhen the induction temperature increases and the density ofthe air in manifold 62 correspondingly decreases.

As shown in FIG. 5, bellows 75 is enclosed ina housing, whose walls arepreferably heat-insulated, connected with induction pipe 62 by means ofa large and short conduit. Eddy currents or turbulence in said conduitand housing caused by the high velocity of `the air ilow in pipfe 62aswell as the pulsations of pressure therein, produce an active thermicexchange, by conduction and convection, between the air flowing in pipe62 and bellows 75. The thermal capacity yof such bellows usually is, ormay be made, extremely small. Therefore, as previously pointed out,the'air ilowingthrough pipe 6 2 and the expansible fluid contained inbellows 75 will have substantially the same temperature.

While the lfuel metering pump describedk above and shown in FIGS. l `and2 offers various advantages, it is no part of the invention covered inthe present application; and it will be understood that, in lieu of saidpump, any other suitable type of injection unit or spray nozzle may beused, such for example as the usual type of nozzle consistingessentially of a calibrated orifice, through which fuel from the fuelmanifold 45 can be injected into the engine induction manifold or otherplace of utilization of the engine. It will be appreciated, of course,that the by-pass or fuel pressure regulating valve 52 or 72 whichcontrols the fuel pressurev in the 'fuel manifold 45 will also controlthe rate of fuel discharge through such nozzles. Where importantvariations in engine induction vtemperature may occur, such as inaircraft engines supercharged for high altitude, according to thepresent invention an arrangement such as that shown in FIG. 6 may beprovided, in which a casing 80, communicating through a large duct 81with induction pipe 62, contains air at induction pressure and, asalready stated in connection with FIG. 5, at induction temperature. Anevacuated resilient bellows 82 in said casing acts on lever 83 tooperate rod 94 and pistons 84, 85 which control admission of oil underpressure, usually `led from the engine lubricating system through pipes87, 88 as indicated by the arrows, to opposite lsides of piston 86.Pipes S9 drains oil back to the engine sump. A floating lever 90 isconnected at its ends with rod 94 and piston 86, and at an intermediatepoint with rod 91 connected through lever 92, rod 93 and lever 74 withfuel pressure regulating valve 72. Also in casing 80 there is a bellows95 which contains a definite weight of gas or other suitable iiud atconstant volume and induction temperature. The absolute pressure in saidbellows is therefore proportional to the absolute induction temperature.Bellows 95 and a similar and evacuated bellows 96 act against each otherand on a lever 97 to operate rod 100 of a servo mechanism similar tothat already described in detail. Engine lubricating oil is led theretoand evacuated therefrom as indicated by the arrows. The pressure of theair in housing 80 acts in opposite directions on bellows 95 and 96thereby b-alancing out the effect of any change of pressure in housing80 so that the load transmitted to lever 97 is only dependent on theinduction temperature. The servo mechanism acts on lever 98 to vary theoperating distance of rod 93y from the fulcrum of lever 92. Spring 99balances the load transmitted by the bellows to rod 100 and is designedso that the operating distance o-f rod 93 from the fulcrum of lever 92is proportional to the actual absolute induction temperature. Anychan-ge in said temperature operates bellows 95 and in turn the servomechanism to rotate lever 98 and Vvary the load of spring 99 until the4balance of rod 4100 in its neutral position is re-established. Mixturecontrol 78, as already shown in FIG. S, is adapted to modify thedistance of rod 93 from the fulcrum of lever 74. The device works asfollows: The evacuated resilient bellows 82 exerts on rod 94 an upwardload proportional to the induction pressure. In normal operation rod 94and control pistons 84 and 85 are maintained in equilibrium in neutralposition by a downward load of equal magnitude transmitted from fuelpressure regulating valve 72 to rod 94. Thus, for a given adjustment oflever 98 and mixture control 78, the induction pressure and the load ofvalve 72 (and in turn the engine fuel supply) are proportional. If nowthe pilot operates the engine throttle indicated 4by numeral 65 inFIGURE 3 to reduce the engine air supply, or if the altitude at whichthe engine operates increases, the induction pressure surroundingbellows 82 decreases, and with it decreases the upward load transmittedby Vthe bellows to rod 94, while the downward load transmitted theretofrom valve 72. remains unchanged.

Bellows 82 thus expands and determines downward motion of the rod 94 andoil control pistons at valves 84 and 85. Oil under pressure, admittedover piston 86, displaces the latter downwardly, causing anti-clockwiserotation of lever 74 and displacement toward the left of valve 72,thereby increasing the open area of the bypass controlled by said valve.The result is that the fuel pressure in conduit 45, and the engine fuelsupply decrease. But also the hydraulic load on valve 72 and in turn thedownward load transmitted from valve to rod 94 decrease, causing rod 94to move upwardly toward its neutral position. Downward movement ofpiston 86 continues until the loads transmitted to rod 94 by valve 72and, through bellows 82, by the induction pressure have once moreattained equal magnitudes and rod 94 resumes its neutral position.Obviously, an increase of induction pressure, due either to a change ofadjustment of the ,throttle control 65 or to a decreased altitude causesthe device of FIGURE 6 to correspondingly increase the engine lfuelsupply. Induction pressure and fuel delivery per cycle thus varyproportionally.

As has already been stated, lever 97 actuated by bellows and 96transmits an upward load to rod 180 which is proportional to theinduction temperature. In normal operation, that is when saidtemperature is constant, said load is balanced by spring 99 and rod 100is in its neutral position. An increase of induction ternperature causesa proportional increase of presure within bellows 95 and of the upwardload transmitted to rod 100. Bellows 95 resiliently expands, bellows 96contracts, and rod 100 `is lifted to a position in which the elasticreaction due to the resilient deformation of the bellows balances thedifference between the upward load transmitted to rod 100 due to thefluid pressure within bellows 95 andthe load of spring 99. Oil underpressure is led above the piston of the servo motor, thus causing lever98 to rotate anti-clockwise and gradually increasing the load of spring99. As the latter load increases, rod 100 moves downwardly. Operation ofthe servo-motor and krotation of lever 98 continues until rod 100reaches its neutral position, the load of spring 99 having ,in the-meantime assumed a value equal in magitude to the new upward loadtransmitted to rod 100 by the bellows and due to the new value of theinduction temperature, the result being that lever 98 assumes a newposition of equilibrium in which `the distance of rod 93 from thefulcrum of lever 92 has increased in proportion to the increase ofabsolute induction temperature.

Thus, the upward load on rod 93 is proportional to the absolute.pressure and inversely proportional to the absolute temperature ininduction pipe 62, and is therefore proportional to the air densitytherein.

If the air charge per cycle, or weight of air present in the enginecylinder during the compression and power 7 Y Y l n strokes, isproportional to the induction density, the mechanism shown in FIGURE 6gives for each adjustment of mixture control lever 78 a correspondingconstant fuel-air ratio.

In certain engines it has been found that the air charge is inverselyproportional not to the absolute induction temperature, but to thesquare root thereof. To automatically maintain in such engines aconstant value of the fuel-air ratio for each position of the mixturecontrol lever 78, the mechanism of FIG. 6 may be modified by theadoption of a spring 101, shown in FIG. 7, whose dellection is, withinthe designed limits, proportional to the square root of the load, suchas a coil spring having a uniform diameter and a non-uniform pitch sodesigned that, within the operating range, the number of free coils isinversely proportional to the spring deflection, whereby the distancebetween rod 93 and the fulcrurn of lever 92 is proportional, and therebythe load on rod 93 inversely proportional, to the square root of theabsolute temperature in induction pipe 62.

In engines in which the air charge is found to be a still differentfunction of the induction temperature, an automatically constant valueof fuel-air ratio may be obtained either by providing resilient means101 of suitable characteristic, or by establishing the suitable relationbetween rotation of lever 98 and distance of rod 93 from the fulcrum oflever 92 by means of a cam substantially as shown in FIGS. 14 or l5.

Furthermore it has been observed that in certain engines, in particularthose highly supercharged and having a large valve overlap, such asapplied conveniently to injection engines wherein it is possible tosecure scavenging of the combustion chamber without loss of fuel, theair charge, or weight of air remaining in the engine cylinder duringcompression and power strokes, is affected, for a given inductionpressure, by the surrounding atmospheric, or exhaust pressure. Tocorrect such influences so that the load on rod 93 be proportional tothe effective cylinder yair charge, a comparatively small bellows, whoseinterior is maintained by means of a suitable conduit at the surroundingatmospheric pressure or substantially at the engine exhaust pressure,may be added to the pressure responsive bellows 82 of FIG. 6, eitherwithin the evacuated bellows 82, as indicated by numeral 102 in FIG. 8,or on opposite side of lever 83, as indicated by numeral 103 in FIG. 9,its size and position being determined in accordance with engine tests.-Passages 102 and 103 provided in the wall of housing 80 maintain thepressure within bellows 102 and 103, respectively, equal to thesurrounding atmospheric pressure.

It is to be clearly understood that, while the fuel metering pumpdescribed above and illustrated in some of the drawings, and thehydraulic control thereof are believed to be particularly suitable forautomatic control, the means for automatically adjusting the fueldelivery or the fuel-air ratio according to the present invention may beapplied to any suitable fuel supply system.` FIG. l diagrammaticallyshows a conventional injection or metering pump of the plunger type 104driven by the engine and comprising a plurality of pump elementsconnected by pipes 105 with the various engine cylinders and whosedelivery is adjusted by axial displacement of control rod 106 connectedwith a spring 107 designed and mounted so that its load is proportionalto the fuel delivery per cycle. Such pump may therefore be operated bylever 74 shown in FIG. 6 in the manner described above.

The device shown in FIG. 6 is used in combination with means operable bythe pilot for controlling the engine air supply, such as means foradjusting the speed of an exhaust-driven turbo-supercharger, or othersuitable means for varying the peripheral velocity of the superchargerimpeller, or, as shown in FIG. 3, a controlI lever 65 operating the airthrottle valve 63.

FIG. 1l diagrammatically indicates an alternative control system whereincontrol lever 108 operable by the pilot adjusts the fuel delivery and adevice having the same character as that shown in FIG. 6 in that itexerts on a rod 93 a load proportional to the air density in inductionpipe `62, or substantially proportional to the air charge per cycle ofthe engine cylinders, operates the means for controlling the engine airsupply, such as the air throttle valve 63, to maintain the fuel-airratio constant or substantially constant at a value determined by theadjustment of the mixture control lever 78. Fuel control lever 108 isconnected through a rod having a lost motion device such as an elongatedslot 109 with lever 111, similar to the lever 55 of FIG. 2, foradjusting the spring load of the fuel pressure regulating valve.Clockwise rotation of lever 111 causes an increase of fuel delivery anda proportional increase of the load transmitted by spring 112 to the rod113 carrying pistons 114 and 115 controlling the admission of oil toopposite sides of piston 116. A tension spring is provided, tending toresiliently maintain, against the action of spring 112, lever 111applied against the left side of slot 109. Oil under pressure from theengine lubricating system is led to pistons 114, 115 and is conductedback to the engine sump as indicated by the arrow. A floating lever 117is connected with piston 116, with lever 64 operating the air throttlevalve 63 and, through a lost motion device such as an elongated slot121, with lever 111. A tension spring 118 tends to rotate the lever 117clockwise, and stops 119, 120 limit its motion. Lever 74', cooperatingwith the rod 93, is connected with rod 113 and transmits to the latter aload proportional or substantially proportional to the air charge percycle. In normal operation the rod 113 is in balance, in its neutralposition, under the action of lever 74 and spring 112 whose load isproportional to the fuel delivery per cycle. 'If the pilot rotatesclockwise either lever 108 to increase the fuel delivery, whichincreases proportionally the load of spring 112, or lever 78 to decreasethe fuel-air ratio, which decreases the torque transmitted by rod 93 tolever 7'4, or if the air charge per cycle decreases owing either toincreased altitude or increased engine speed, in which latter case theautomatic device of FIG. 6 proportionally decreases the load transmittedto lever 74 by rod 93, the rod 113 is displaced to the right to admitoil under pressure to the left side of the piston 116 and thereby rotatethe lever 117 clockwise to open the air throttle valve 63 and increasethe flow of air, which in turn increases the induction air density, andthe cylinder air charge. The device shown in the upper part of FIG. 6causes the load transmitted by rod 93 to the lever 74 to increaseproportionally, thus bringing rod 113 back toward its neutral position.Displacement of piston 116 of the servo-motor goes on until the balanceof the rod 113 in said neutral position is again attained. This meansthat in the lirst case, in which the pilot rotates clockwise the controllever 108 to increase the engine fuel supply, the combined servo-motorsshown in the upper part of FIGURE 6 and in FIGURE ll automatically openthe air throttle to proportionally increase the engine air supply,thereby maintaining the fuel-air ratio constant. In the second case, inwhich the pilot rotates the mixture control lever 78 clockwise, the aircharge is automatically increased so as to bring the fuel-air ratio to alower value corresponding to the new adjustment of the lever 78. In thethird case, in which the air charge decreases owing to increase inaltitude, or increase in engine speed and corresponding reduction inengine volumetric eciency, said device automatically increases theopening of the throttle to maintain the fuel-air ratio constant at thevalue corresponding to the setting of the mixture control lever 78. Thedevice will obviously operate in the opposite Way when the pilot rotatesthe lever 108 or .the lever 78 anti-clockwise, when the altitudedecreases, or when the engine speed decreases.

It is therefore clear that, while the device shown in FIGURE 6, intendedto be used in connection with an engine in which the pilot directlycontrols the engine air supply, automatically adjusts the engine fuelsupply so as to maintain the fuel-air ratio constant at a valuecorresponding to the setting of the mixture control lever 78, thearrangement combining the upper part of FIG- URE 6 with the device shownin FIGURE ll, intended tov be used in connection with an engine in whichthe pilot directly controls the fuel supply, automatically adjusts theair supply thereof to keep the fuel-air ratio at a value correspondingto the adjustment of the lever '78. In both cases the pilot controls thesupply of one of the components of the combustible mixture, while theauto matic device adjusts the supply of the other component in such away that the fuel-air ratio is determined by the setting of a mixturecontrol member 78.

However, in the operation of the device shown in FIGURE 1l, especiallyat high altitude, the lever 117 may reach the stop l119, in whichposition the air throttle valve `63 Vis wide open, before the rod 113 isled back to its neutral position, and the piston 116 will be furtherdisplaced to the right to rotate the levers 117 and 111 anticlockwiseand decrease the fuel delivery until the fuel-air ratio assumes thevalue corresponding to the adjustment of lever 78 and the balance `ofrod 113 is attained. Inverse operation of the devicewill occur wheneither lever 108 or lever 78 are rotated anticlockwise or the air chargeper cycle tends to increase` FIG. 12, a partial Vmodification of FIG.11, shows a lever 123 which, like lever :111 of FIG. ll or lever 55 ofFIG. 2 controls the spring load of the fuel pressure regulating valve.`A load `proportional to the fuel delivery per cycle is transmitted `torod 113 by a plunger 124 whose inner end is exposed to the fuel pressureof conduit 45, and on which a highly resilient lspring 125, similar tospring 73 of FIG. 4, exerts a substantially constant pressure balancingthe fuel pressure on the plunger 124 corresponding to `zero fueldelivery.

Obviously, the same device of FIG. 11 may be applied to a conventionalinjection or metering Vpurnp -4 shown in FIG. 13 in which the lever 127,controlled by way of likages including elongated slots 109 and 121 andconnected with spring y112 controls by means of a -rod 1196 the fueldelivery per cycle of pump 1104, the arrangement being such that whenrod 1.13 yis 'in neutral position, the load `of spring 112 isproportional to the fuel delivery per cycle.

The above arrangements, yin which the adjustment of fuel-air ratio ofthe Vcombustible mixture is left to the arbitrary choise of the pilot oroperator, is not the most suitable in connection .with aircraft engines.As it has already been stated, `engine tests show that the most suitablevalue of fuel-air ratio varies with the engine operative conditions,ramong which are the air `pressure or density in the induction manifold,the engine speed, the engine cylinder temperature. Accordingly, one ofthe objects of the invention is to provide, in combination with thepreviously disclosed arrangements, means responsive to one or moreengine operative conditions whereby the adjustment of the mixturecontrol member, and in turn the fuel-air ratio, may be automaticallycontrolled and vary as a predetermined function of said operativecondition or conditions.

Operation of the engine with best economy ymixture is possible overacertain range of power, beyond which the engine cannot Vsafely beoperated without resorting to someadditional enrichment of the Amixtureyto suppress over-heating and Adetonation. A temperature responsiveelement 131i, FIG. `14, mounted in suitable location such as on acylinder 'head or near an exhaust port, is connected with a bellows 131placed to act against an evacuated bellows v132 so that changes in thepressure surrounding the bellows act in opposite directions on saidbellows and therefore have no effect on their operation. Temperaturechanges about element operate the bellows 131 and in turn the rod 133 ofa servomechanism, similar to those already described in detail, tocontrol the angular adjustment of lever l134, of cam 135 and to vary theload of spring 136 acting on the rod 133. An increase in temperature ofthe element 130 lowers the rod 133 and in turn rotates the lever 4134clockwise thereby increasing the load of spring 136 until the balance ofrod 133 in its neutral position is rees tablished. The cam 135 isadapted to operate lever 137, having the same function as lever 79previously illustrated, so that, for each temperature of element 130, itdetermines a corresponding predetermined minimum possible value of thefuel-air ratio. Mixture control lever i3 and lever 137 are connectedthrough a lost motion device such as an elongated slot 138 and a tensionspring 139 whereby the lever 78, whatever its adjustment may be, doesnot oppose anticlockwise rotation of lever 137 when the latter isoperated by the cam 135.

It has been pointed out in the foregoing that the device illustrated inFIG. 6 may automatically vary the engine fuel supply per cycle in directproportion to the air induction pressure and in inverse proportion tothe absolute temperature thereof, the proportionality ratio, and in turnthe fuel-air mixture ratio being determined by the elfective length ofthe horizontal arm -of the bell crank lever 74, or in other words by thedistance between rod 93 and the pivot of lever 74. lt has also been setforth that such a device will operate correctly as stated with an enginein which the cylinder air charge varies proportionally to the airinduction density, but that in certain types of engines, for instancehighly supercharged and air scavenged aircraft engines, the effectivecylinder air charge is appreciably affected by changes of exhaust orsurrounding atmospheric pressure, and may vary with the induction airabsolute temperature according to a function of the latter substantiallydifferent from inverse proportionality, land that in combination `withysaid engines devices partially modiied according to FIGS. 7, 8 or 9will therefore be more suitable. However, whether or not it includes anyof said modifications, the device of FIG. 6i is provided with manuallyactuatable control means 78 for adjusting the effective length of thelever 74 to control the fuelair ratio. In order to obtain, as statedamong the ob- 'ects of the invention, a fuel-air ratio that variesautomatically as a predetermined function of engine operativeconditions, the lever 79 of the device represented in FIG. 6 may beeliminated, and in substitution therefor there may be provided a .lever`137 actuated by a cam having two distinct ways of adjustment, forexample a slidable and rotatable cam 146 as shown in FIGS. l5 and 16,there being provided means responsive to engine operative conditions foradjusting said cam in said two `distinct ways, whereby the mixture ratiomay automatically be caused to vary as a predetermined function of twoindependent variables, said function being dependent on theconfiguration of the cam.

The upper arm of lever 137 is connected with the lower end of rod 93,shown `in FIG. 6, for adjusting the effective length of lever 74, andhas therefore the same function as the upper arm of lever 79. The lowerarm of lever 137 has a lost motion connection with a rod 138 which maybe actuated by Way of the manual control member 78 of FIG. 6. A third,horizontally extending arm of the lever 137 shown in FIGS. l5 and 16 isactuated by the cam 146 which may be axially and angularly adjusted byengine condition responsive devices, shown in FIGS. `l5 and 16 asmechanisms responsive to the engine speed and to the manifold airpressure respectively.

The automatic mixture ratio control device may thus include themechanism of FIG. 6 minus lever 79 in combination with the structurerepresented in FIGS. 15 and `l6. FIG. 15 shows means for regulating thefuel-air ratio as a function of the induction pressure, assuming themixture control lever 78 to be in lean adjustment, with rod 138 in theposition shown in the drawing, thus permitting contact between thehorizontal arm of lever 137 and cam 146. A bellows 141, evacuatedtotally or in part, and enclosed in a housing communicating with engineinduction pipe 62, operates rod 142 of a servo mechanism similar tothose already described, whereby an increase in induction pressureraises rod 142 and causes lever 143 to be rotated anticlockwise untilthe increased load of tension spring 144 re-establishes the balance ofrod 142 in its neutral position. Lever 143 is secured to an externallysplined sleeve 147 rotatably mounted on an engine driven shaft 145. Thewarped cam 146 is slidably but non-rotatably mounted on sleeve 147, sothat the angular adjustment of the cam is dependent on the inductionpressure, while the axial adjustment of said cam is determined by speedresponsive means such as a governor 148 dliven from the engine throughshaft 145. The governor 148 controls rod 149 of a servo mechanismwhereby an increase in engine speed displaces rod 149 to the left andcauses lever 150 to be rotated clockwise until the increased load oftension spring 151 returns the rod 149 to its neutral position. The cam146 therefore determines for each value of induction pressure and enginespeed a corresponding minimum possible value of fuel-air ratio. In thepreferred embodiment the form of the cam is such that in the cruisingrange of induction pressure and engine speed combinations such minimumvalue corresponds substantially to the best economy mixture, while forcombinations of engine speed and induction pressure corresponding tohigher power output the minimum fuel-air ratio will be higher than thatcorresponding to best economy mixture. Automatic van'- ation of themixture ratio is obtained by means of the cam 146 whenever the mixturecontrol lever 78 is set for lean mixture, owing to the elongated slot138 and spring 139, while further enrichment may be obtained by movingthe lever 78 anticlockwise.

It is to be expressly understood that the invention is not limited tothe specific embodiments shown, but may be used in various other ways,and changes, modifications, substitutions, additions and omissions maybe made in the construction, arrangement and manner of operation of theparts without departing from the limits or scope of the invention asdefined in the following claims. Where the claims are directed to lessthan all of the elements of the complete systems disclosed, they areintended to cover possible uses of the recited elements in installationswhich may lack the non-recited elements.

I claim:

l. In a control device for an engine having an air induction system anda fuel supply system with fuel conduit means and valve means therein forregulating the rate of engine fuel supply, the combination with saidvalve means of air induction pressure responsive means, air inductiontemperature responsive means and engine speed responsive meansoperatively connected to said valve means for actuating the same tocontrol the rate or' engine fuel supply as a predetermined function ofsaid pressure, temperature and speed.

2. In a fuel supply system for an engine having an air induction system,the combination with valve means for regulating the rate of engine fuelsupply, of engine speed responsive means, induction air pressureresponsive means, induction air temperature responsive means andmanually operable control means for actuating said valve means tocontrol the rate of engine fuel supply as a preselected function of saidspeed, pressure, temperature and the setting of said manual controlmeans.

3. For an engine having an air intake system and a fuel supply systemincluding a variable-pressure fuel conduit through which liquid fuel isdelivered to the engine at a rate dependent on the fuel pressure in saidconduit, the combination with valve means associated with said conduitfor variably regulating the fuel pressure therein, of intake airpressure responsive means, intake air temperature responsive means andengine speed responsive means operatively connected to actuate saidvalve means for regulating the fuel pressure in said conduit as apreselected function of said speed, pressure and temperature.

4. For an engine having an air intake system and a fuel supply systemincluding variable-pressure fuel conduit means through which liquid fuelis supplied to the engine at a rate dependent upon the fuel pressure insaid conduit means, the combination with pressure-regulating valve meansfor controlling the fuel pressure in said fuel conduit means, of intakeair pressure responsive means, intake air temperature responsive meansand engine speed responsive means and manually settable control meansoperatively interconnected to actuate said valve means for regulatingthe fuel pressure in said conduit means as a preselected function ofsaid speed, pressure, temperature and the setting of the manual means.

5. In control apparatus for an engine having an air induction systemwith air flow control means therein, a fuel supply system includingvariable-pressure fuel conduit means through which fuel flows to theengine at a rate dependent on the fuel pressure therein, the combinationwith pressure-regulating valve means under the control of the operatorfor controlling the fuel pressure in said fuel conduit means, of fuelpressure responsive means connected with said fuel conduit means forsensing pressure variations therein, engine induction air pressureresponsive means, engine induction air temperature responsive means, andan operative connection for actuating said air ow control means fromsaid fuel pressure responsive means and said air pressure and airtemperature responsive means.

6. Engine control mechanism including a fuel injection system, meansconnected with said system for controlling the engine fuel supply,engine air supply control means, and means for actuating said air supplycontrol means in dependence upon the engine fuel supply and the engineinduction air pressure and temperature.

7. Engine control system including manually operable means forcontrolling the engine fuel supply, engine air supply control means, andmeans for actuating said air supply control means in response tovariations of engine fuel supply and induction air pressure andtemperature.

8. In a fuel supply system including variable-pressure fuel conduitmeans through which liquid fuel is supplied to the engine at a ratedependent on the fuel pressure in said conduit means, the combinationwith a fuel pump for supplying fuel to said conduit means, of valvemeans for regulating the fuel pressure in said conduit means, and meansresponsive to speed, pressure and temperature conditions of said enginefor acting on said valve means to control the rate of engine fuelsupply.

9. In a fuel supply system for an engine having an air intake system,said fuel system including variable-pressure fuel conduit means throughwhich liquid fuel is supplied to the engine at a rate dependent upon thefuel pressure in said conduit means, the combination with a fuel pumpfor supplying fuel to said conduit means, of valve means for regulatingthe fuel pressure in said conduit means, air intake pressure responsivemeans for acting on said valve means to vary said fuel pressuresubstantially in proportion to said air pressure, and means responsiveto temperature and speed conditions of the engine for acting on saidvalve means to vary said fuel pressure in predetermined relation to saidtemperature and speed conditions.

10. In control apparatus for an engine having an air induction systemfor supplying air flow to the engine, and a liquid fuel supply systemwith a variable-pressure fuel manifold and spray nozzles connected withsaid fuel manifold for supplying the engine with liquid fuel at a ratedependent upon the pressure in said fuel manifold, the combination witha fuel pump for delivering fuel to said fuel mani-fold, of valve meansfor controlling the fuel pressure in s'aid fuel manifold, and meansresponsive to variations of air induction pressure and atmosphericpressure and means responsive to speed and temperature conditions of theengine for acting on said valve means to control the pressure in saidfuel manifold.

11. An engine fuel metering system comprising: a fuel pump adapted to bedriven fromy the engine; fuel pressure actuated fuel ilow controllingvalve means responsive to changes of fuel pressure on the discharge sideof said pump for regulating the rate of fuel delivered by the pump tothe engine; and means operatively connected with said valve means foractuating the same, including: a closed housing adapted to be connectedwith the engine air induction system, a pressure responsive bellowsassembly in said housing including a larger bellows which is evacuatedand a smaller bellows which is internally vented to atmosphericpressure, means responsive to changes of temperature in said airinduction system, and speed responsive means adapted to be driven fromthe engine.

l2. An engine fuel supply system including an engine driven fuel pump;fuel delivery control means for regulating the engine fuel supply;engine air induction pressure and atmospheric pressure responsive means,engine air induction temperature responsive means, and engine speedresponsive means' for actuating said fuel delivery control means; saidfuel delivery control means including a resiliently loaded slidablevalve actuated by fuel pressure variations on the discharge side of saidfuel pump and operatively connected with said speed responsive means.

13. Engine fuel supply system including an engine driven fuel pump;control means responsive to fuel pressure on the discharge side of saidpump for regulating the rate of delivery of fuel from said pump to theengine; and means including engine speed responsive means, engineoperative temperature responsive means and means responsive to changesof atmospheric pressure and acting on said control means in oppositionto the fuel pressure applied thereon for positioning said control means.

14. Engine fuel supply system including an engine driven fuel pump;delivery control means for varying the quantity of fuel supplied by thepump to the engine, including valve means responsive to fuel pressure onthe discharge side of said pump; and means, including operativelyinterconnected engine speed responsive means, engine operatingtemperature responsive means and a manually operable control lever forapplying a variable load to said valve means in opposition to said fue]pressure, to position said valve means.

15. Engine fuel supply system including a fuel pump; control means forregulating the rate of fuel supply from the pump to the engine; saidcontrol means including valve means responsive to fuel pressure on thedischarge side of the fuel pump; engine induction air pressureresponsive means acting on said valve means in opposition to said fuelpressure for positioning said valve means; and means including enginespeed responsive means for varying the effect of said induction airpressure responsive means on said valve means.

16. An engine having `an air induction system; a variable-pressure fuelsupply system whose delivery increases or decreases with the fuelpressure; a valve in the fuel system; air pressure responsive meansconnected with the induction system to actuate the valve; air densityresponysive means connected with the induction system to actuate saidvalve; and means for actuating said valve in response to variations ofsaid fuel pressure.

17. For use with -an air-consuming combustion engine having an airintake system, a fuel system including: a fuel supply pump; meansmovable in response to variations of fuel pressure on the discharge sideof said pump for varying the delivery of fuel by said pump tothe engine;a pressure sensitive device adjusting by its movements the means forvarying the delivery of fuel to the engine, said device including intakeair pressure responsive means, intake air temperature responsive means,and engine speed responsive means.

18. In a fuel control for a thermal powerplant, a hydraulic cylinderwith a slidable piston defining a pressure chamber, means for supplying-a control iluid under pressure to said chamber, means for varying thefuel supply rate in accordance with changes in the quantity of controlfluid in said chamber, a spring adapted to bias said piston `against thepressure of the control fluid, rst means including a pilot valveconnected to the piston by a follow-up lever for controlling thequantity of control fluid admitted to and released from said chamber, avariable ratio lever mechanism connecting the spring to the piston, andmeans including a servo-motor connected to said mechanism and operableto vary the effective lever ratio in response to changes in a controlpressure which is a function of ambient atmospheric pressure.

19. A fuel and speed con-trol apparatus for a combustion engine havingan air compressor, and a pump for supplying fuel to said engine;comprising a manual control lever and a fuel regulating system forcontrolling the delivery of fuel from said pump to said engine; saidsystem comprising a fuel metering orifice having a variable flow areaand first fuel control means responsive to the discharge pressure ofsaid compressor, second fuel control means responsive to the position ofsaid manual control lever, and a third fuel control means responsive tothe engine speed for varying the ilow area of the same fuel meteringorifice to control the rate of supply of liquid fuel to the engine.

20. A fuel and speed contro-l apparatus for a combustion engine having`an air compressor, and a pump for supplying fuel to said engine;comprising a manual control lever and a fuel regulating system forcontrolling the delivery of fuel from said pump to said engine; saidsystem comprising a fuel metering orifice having a variable flow area,first fuel control means responsive to the discharge pressure of saidcompressor for varying said variable flow area in accordance with saidpressure, second fuel control means responsive to said manual controllever for varying said variable ow area in response to changes in theposition of said lever, and third fuel control means responsive toengine speed for varying said variable iloW area in accordance with saidspeed.

References Cited in the le of this patent UNITED STATES PATENTS2,004,869 Hogg June 11, 1935 2,088,954 Gregg Aug. 3, 1937 2,177,120Schaeren Oct. 24, 1939 2,214,766 Hurst Sept. 17, 1940 2,217,364 Halfordet al. Oct. 8, 1940 2,245,562 Becker June 17, 1941 2,274,693 Heinrich etal Mar. 3, 1942 2,290,921 Udale July 28, 1942 2,341,257 Wnsch Feb. 8,1944-

